From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ipmail07.adl2.internode.on.net ([150.101.137.131]:16165 "EHLO ipmail07.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752620AbeFGFci (ORCPT ); Thu, 7 Jun 2018 01:32:38 -0400 Received: from dave by dastard with local (Exim 4.80) (envelope-from ) id 1fQnXI-0004uH-5G for linux-xfs@vger.kernel.org; Thu, 07 Jun 2018 15:32:36 +1000 Date: Thu, 7 Jun 2018 15:32:36 +1000 From: Dave Chinner Subject: Re: [PATCH 1/2] xfs: setup VFS i_rwsem lockdep state correctly Message-ID: <20180607053236.GR10363@dastard> References: <20180607052132.6207-1-david@fromorbit.com> <20180607052132.6207-2-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180607052132.6207-2-david@fromorbit.com> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: linux-xfs@vger.kernel.org On Thu, Jun 07, 2018 at 03:21:31PM +1000, Dave Chinner wrote: > From: Dave Chinner > > When lockdep is enabled, it changes the type of the inode i_rwsem > semaphore before unlocking a newly instantiated inode. THere is the > possibility that there is already a waiter on that inode lock by the > time we unlock the new inode, so having lockdep re-initialise the > lock is a vector for trouble. > > Avoid this whole situation by setting up the i_rwsem lockdep class > at the same time we set up the XFS inode i_ilock classes and so the > VFS doesn't have to change the lock class itself when it is > potentially unsafe. > > Signed-Off-By: Dave Chinner I just realised that the VFS equivalent patch has made it upstream, too, which would help explain this a bit more. Darrick, can you add this to the commit message: "This change is necessary because the equivalent fixes to the VFS code made in commit 1e2e547a93a0 ("do d_instantiate/unlock_new_inode combinations safely") are not relevant to XFS as it has it's own internal inode cache lookup and instantiation routines." Cheers, Dave. -- Dave Chinner david@fromorbit.com